


Under Kindness I Fell

by Dark_Crystal_Demon



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Blood and Gore, Body Horror, Bondage and Discipline, Consensual Sex, Dubious Consent, Master/Slave, Multi, Non-Consensual Bondage, Psychological Horror, Rape/Non-con Elements, S&M, Suicide Attempt, Underfell Asgore Dreemurr, Underfell Grillby, Underfell Monster Kid, Underfell Muffet, Underfell Papyrus, Underfell Reader, Underfell Sans, Underfell Toriel - Freeform, Underfell W. D. Gaster, Voyeurism, reader is female
Language: English
Status: In-Progress
Published: 2017-10-08
Updated: 2017-10-08
Packaged: 2019-01-10 13:56:17
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Rape/Non-Con
Chapters: 1
Words: 4,616
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12300528
Author URL: https://archiveofourown.org/users/Dark_Crystal_Demon/pseuds/Dark_Crystal_Demon
Summary: An Underfell Verse with a touch of horror, a lot of gore, and an explicit amount of dark desires. You are a green soul tortured by your past, present, and probable future. Cursed with an inability to die from mortal wounds, you become the target of malice, curiosity, and lust while trying to survive this twisted world of monsters. Be careful you don't become twisted yourself.Warning: this is my own personal rendition of the Underfell Crew: dark, terrible, and without restraint - and that includes Reader... eventually. This is not a fic for everyone. Please heed the warnings and tread lightly.





	Under Kindness I Fell

**Author's Note:**

> I just want to take a moment to apologize to everyone for starting a new fic. I couldn't shake the images from this story and had to write it down so that it would leave me alone. 
> 
> So welcome to a demon's dreams of an Underfell Verse...

You sit in your cell and listen to the footsteps coming down the dusty stone hallway of the lab’s underground prison. Some humans scream while others cry, but you wait patiently on your cot. Legs crossed beneath you in meditation, you smile as his footsteps stop in front of your bars. Your thoughts settle on the last sentence of the chant inside your mind:  _It is time to change your destiny._

Keys jingle and you open your eyes at the skeleton who found you months ago when you'd fallen inside the mountain. You know him as Sans, but many of the humans - at least the ones who could still talk - down here would call him the Master’s Hound, a deadly hunter in the woods of Snowdin. Rumors whispered between cells claim that he can smell living meat from a mile away even during a snow storm. He navigates the Master’s traps with a casual grace that is enviable to those maimed and captured by the same. And when he finds you, his callous treatment of humans is echoed through the barren woods and repeated by quivering lips of the residents under this lab. 

But even the darkest whispers would agree that the Hound’s rough retrieval is nothing compared to the Master’s blood lust or the Mad Doctor’s experiments in this world of nightmares.

You understand the fear your neighbors have of your captors. The Master, Mad Doctor, and Hound are nothing anyone would have believed were real: walking skeletons with razor sharp teeth, clawed limbs, and magical abilities that could flatten your body into an ungodly pancake or impale your corpse with a thousand magical bone spears. They are some of the most powerful monsters in the underground, and you... you've survived more of their horrors and dark desires than any other human in this prison. For that, you are isolated from the other humans, but you no longer think of those "fragile flesh bags" as your peers. They despise you for living, but they cannot comprehend what happens to you when you're taken from this cell. In their ignorance, they call you a whore, but the truth is far more insidious. 

You are cursed, and it's turning you into a monster. 

In your past, you'd always been told your kindness would be the end of you. They had been right, and you wish now that you had listened. Maybe then you wouldn't be where you are, paying for deaths that you can never heal... Sometimes you can still hear the screams of children from that awful day. You could hear those screams as you ran away from the carnage... from the destruction  wrought by a person you had taken care of. You ran out of the building and up the mountain pass. You jumped over the safety gate and ignored the warning signs within Mourner's Cave. The wails of ghosts echoed in the darkness, but scientists believed that it was only the way the wind whistled through the tunnels. You felt at peace when you found the hole known as Lover's Leap. You'd always felt drawn to it and now you knew why, because it was your destiny too. You couldn't live with yourself after what you'd witnessed... what you helped create. 

You jumped... but the universe didn't accept that as payment for your sin. It had bigger plans for your punishment. 

You felt the ground as it smashed against your body. You felt your bones break and your heart stop and then... green light surrounded your vision as a warm tingling came to each of your wounds and brought your heart back to life. Bones reset painfully and then jolted you with intense energy as they fused back together. It was an adrenaline rush that leapt you to your feet, but had no way of getting you out of the world you had fallen into... a world of monsters that fed off humans and hate. 

It is a world that would try to kill you a hundred times within the next few weeks as you searched for your way out of those caves. And when you finally broke free of that dark confine with its evil queen, the fake sunlight of the underground deceived you into thinking you might be safe. But you weren't. You'd never be safe again. In this world, deadly traps laid waiting on the most innocent looking paths. Before you could blink, you would be impaled with a spear against a tree or agonizing under the teeth of a giant bear trap.

It was under such a trap that Sans had found you. The Hound had smelled your blood.

"That's gotta hurt," he grunted as he looked at your leg mangled in metal. You thought he must be the grim reaper himself, bloodied fur hood framing his skull and a sled of two frozen corpses pulled behind him. His wicked smile only perpetuated the image as you tried rip your leg from the trap and get away. "Lots of energy for someone who's lost so much blood."

"Stay away from me!" You swung a large stick in his direction. It had been the spear from earlier, but it's tip had broken off, embedded in the tree, so it wasn't very threatening, especially when you had to hop not to lose your balance.

"You're not really in a place to make demands," the red eye lights in his skull gleamed in their mockery. His boots crunched in the snow as he closed the distance between you. He dodged each of your attacks with a speed that made him look like he wasn't moving at all. You'd think you were about to hit him and then... it was like it passed right through him. "I like your spunk, kid, but I'm way outta your league."

You stood your ground as he stopped your last attack by grabbing your wrist. He crushed the bones in your hand until you let go with a yelp. You glared at him. He wasn't much taller than you and your eyes could see straight past the red eye lights into the black eye sockets of his skull. You expected to see the bony back of his head in there, but no light entered those sockets nor the gaping hole that was his sneering mouth. 

"Anyone tell you it's rude to stare?" he asked, pushing you to the ground. You gasped for air as the wind left your lungs upon impact with the snow against your back. The unpleasant chill of ice melting through your already tattered clothing made you shiver. 

Sans didn't bother to acknowledge your pain or notice as your hand repaired itself. You hid it under the snow just in case, but lost the rest of your thought process as Sans pried open the bear trap with his bare, bony hands.

"AHHH!" you screamed, jolting upright, and then fell back in relief as your leg started to heal. It was euphoric every time your body became whole again. 

"That's new," Sans grunted, staring in disbelief at your blood covered, but now perfectly healed, leg. You take the moment of surprise to tap into the adrenaline realignment always gives you and kicked him straight in the face. 

You're surprised you succeed; your foot cracked against his hard skull. He stumbled back, falling on his ass and cradling his jaw. You turn around and make a dash for the thickest part of the woods you can see. 

He tackles you before you can even clear the first bush. Your face falls into the branches and gets torn apart by its unforgiving twigs and razor sharp leaves. You moan into the dirty snow of the ground. Its cold irritated your wounds and it reflected the green glow of your magic as you healed again. You squirm under the weight of the skeleton, but he turns you around easily, pinning your arms and legs with his own. His eyes danced across your face, bloodied and wet from the fall, but without a trace of the cuts that had just been made. He sniffs the air with a nose he doesn't have. 

"You smell like a human. You look like a human," he bends down closer, his eyes beginning to flare like fire. A magical red tongue you hadn't seen before emerges from his mouth and licks your bloody cheek. He hums in approval. "You taste like a human. So... how can you do magic, kid?"

His demeanor had changed. Despite his words, he now seemed more like the child. His apathy  replaced with an inquisitive expression you knew only too well. That look reminded you of a place that no longer existed for you any more. You had almost forgotten it in your continued fight for survival. A part of you hated that he had just reminded you of what you lost... what you had chosen to lose... when you jumped and landed in this hell. You didn't owe this monster any explanations. Not that you had any. You spit in his face instead and enjoyed watching that curious look disappear into a grimace. You preferred the more hostile emotions. They were easier to deal with in this world. Anything else just gave you a hope that you've learned can't be real in this world.

"Don't want to talk? Fine. The Doc will figure it out."

Anytime you think back on that moment, you wonder what would have happened if the Doctor really had been the next skeleton you met. You're sure you would not still be living. The Doctor is forced to hold back on many of his experiments because of your Master. He's cut you open a thousand times, taken out each organ, recorded your death, and marveled at the way your body regenerates. He's blooded you, burned you, and chomped off limbs to see how fast they regrow. But he's never tested what would happen if he incinerated you, or if your body would come back after months of being smashed under a boulder. You know the Doctor's curiosity has no end and his empathy has no beginning - not for humans anyway. Not even for monsters. As far as you know, the only beings the Doctor even knows exist are his sons. Everything else is just a part of his eternal list of science projects. If his younger son hadn't laid claim to you, its a certainty that the Doctor would not have shown the restraint that he has... nor become as creative. Death would be welcome to the darker desires he can perform with a body that won't die. 

But the sexual appetites of the father are nothing compared to the son who found you in the cell waiting for your time in the lab. Your Master was looking for warriors for his "games." Your body type would not have qualified at the time, but your Master had a keen eye. He saw your body covered in blood but unblemished underneath. He walked right into your cell and inspected the areas himself in front of countless humans who didn't dare move while he tore away your clothes and demanded in a loud booming voice, "HUMAN, WHERE ARE YOUR WOUNDS?"

Your only response was a cry of pain because he was gripping your arm so tightly in his inquiry that the tips of his claws pierced your skin. He released you with an irritated huff, "I forget how fragile humans are-" But stops speaking as you sigh in relief, your arm glowing, and your eyes closed as the tiny wave of euphoric alignment washed over you. It wasn't as strong a wave as when your leg had been repaired earlier, but it still sends a shiver over your body. You open your eyes to the skeleton grabbing hold of the sides of your face. 

"BURIED TREASURE!" he yelled out to no one but nearly made you deaf with his face so close to yours. He carried you out of the cell and your fate was sealed.

You’d become the Master's favorite play thing. He insisted on bringing you with him to most of his favorite events. You sat on his black leathered knee and watched his gladiator “games” while he fondled you at the most inappropriate times. His fist squeezed your breast and fingers dug inside you as blood spilled on the ground. He enjoyed making you bleed as well; licking his fingers as he called for the next match. Since you healed so fast he could reopen the same wounds multiple times in an event. And when he came back from a match of his own in the arena, the blood of his opponents mixed with yours as he took you in front of the entire stadium... You are sure some monsters came to the games just to watch you scream as he tears you apart with his desire. You can see the hungry looks in the other monsters - and the disgust in the faces of the humans who have survived that day. They’re not disgusted by the Master. It’s the smile on your face as you heal during the process that never sits well with them.

You learned that you aren’t the first green soul with healing magic to fall into the mountain, but you are the first strong enough to withstand the whims of the skeletons. Most green souls that had any magic healed others... your magic selfishly only healed yourself. It made you notorious in the cells. 

"The Skeletons' Whore," they'd call you as dozens of humans would be sent to the Doctor in a week, but you're the only one that ever returned to the cells. Your Master would call for multiple humans in his games, but only you would return unscarred and covered in blood that wasn't always yours... And the Hound...

The Hound never touches you. 

"Is it time for my walk?" you ask Sans from your cot. You usually don't speak first, but he is being unusually silent. No bad joke or pun greets you today. Just the jingle of keys and his silent form standing in the doorway. 

"Boss says you want to change your routine," Sans never calls his brother by his name. He gestures to your leash, hanging on the wall. It floats from its hook to his hand. You stand up, obediently walking towards him and presenting your neck, where his brother's collar lay. "He says you want to be in the games."

He isn't asking you a question, but his curiosity is easy to read. He's the monster you've spent the most time with since you've been down here. The family errand boy and you were frequently his chore.

"I'm glad my Master approves my request. I hope you do too?" You whisper the last line.

Sans gives you a slight nod in. You both know it's not his place to approve or disapprove. The Hound's job is to watch. When he isn’t sleeping, he spends most of his time trying to make sure his family is happy and their needs are met - whatever needs they may have. 

You learned about his role quite quickly when you were presented to him after your first evening with his brother. Tears stained your cheeks, blood crusted on your skin, you were a mess. You nearly missed the surprised look on the face of the skeleton who had brought you here. Your new Master reprimanded him for hiding such a treasure. "YOU KNOW HOW MUCH I LOVE HUMANS AND THIS ONE WON'T DIE!" 

After his brother had thoroughly scolded him, Sans was ordered to clean you up and give you your own cell. He'd been your caretaker ever since. It didn't mean much at first. He was just your escort to and from your next torture session. But over time, your magic grew stronger and the pain became less prominent. You decided the only way you could be free is if you fell into the role of obedient servant and dutiful experiment. From your Master, the Champion of the King's Royal Guard, you learned about the court and politics. From the Doctor you learned about magic and science. But you were caught off guard the first time the Hound brought you a burger for your dinner... or left a book case in your cell... or gave you a journal to write in.

"You won't make any friends down here by joining the games," he whispers, a soft chuckle on breath as you smile up at him. Your heart beats faster from seeing the concern he won't say, but hides in the corner of his eyes that aren't smiling.

"I don't care about what humans think," you reach up and run your fingers along his own spiked collar as he finishes fastening your leash. 

"Hey,” he jerks his head away with a warning in his clipped tone. 

You don't apologize, but you drop your gaze. You lower your hands to your own collar. 

"You can't do things like that," he adds in a grumble, betraying himself as he continues to talk. "You know that, right?"

You don't answer. He won't demand you to speak. That's not his role. Your obedience is mandated by the other members of his family, but he... you reach up again and touch his collar. Sans' fist clenches the worn leather of your leash. You step forward so that his hand rests between your breasts. You feel his bones shake, but he doesn't move...

He always thinks of everyone but himself. Or at least... he pretends to. When his brother claims you in the arena or when his father loses himself within you on his lab table, you see Sans... watching.

The Hound enjoys watching... but that's all he's ever granted. The needs of pets are usually neglected...

Sans gives a snort, coming back to his senses by tugging your leash to bring your head down and your eyes away from his face. "Stupid."

You know he's right. But you've found your hope again, and it is making you bold. You are about to step onto the path that will change your destiny in this world... and you are determined to change his as well.

But until then, you follow his lead and ignore the spit and murmured insults from the denizens of the other cells. "Monster whore." "Bloody demon." "She can't be human."

Human. Monster. The delineation between the categories has become blurred the longer you stay here. Humans didn't last long. You didn't even bother to learn their names anymore. They are just slaves, primitive beings who only knew how to use force to get what they want. The monsters have magic. It is integrated in every part of their being; making skeletons walk, talk, and fuck... 

You stopped associating yourself as human long ago. You are a treasure, above them. You are kept in the cells only because your Master needs to keep up pretenses. He's one of the rulers of this world as the prize warrior of the Royal Guard. His father is the Royal Scientist. His brother...

You look at the back of Sans' dirty and scarred skull, outlined by the fur of his hoodie he hadn't bothered to pull up.

Sans doesn't have a fancy title, but his reputation in the monster world is just as deadly as the Hound persona he's known as in the cells. Monsters call him "Red." It's the last color a monster will see before they're dusted: the red pin pricks of light within Sans' eyes. To monsters, he is the silent assassin, appearing from no where and eliminating any who plot against his family. He hunts in the urban sprawl of the underground with the same efficiency that he does in the woods. It is a monster's mistake if they believe he is really just sleeping in that restaurant booth or on the bench by the side of the street.

You want to be as frightening as the Hound. Your Master thinks your desire to be in the games is only to please him, but your desire goes much further than that. You want to slay your Master's enemies. You want to see fear in monster and human alike. You want to earn a place in the house and outside of the cells. You want... to stop surviving as only a pet in this world. You want to run the streets with the freedom only power can give you. And you want...

Sans pauses for a moment at the top of the stairs in the slave transport lobby. "Are you sure you want to do this?"

"Master will soon get bored if I don't learn new tricks," you answer.

"You won't be given armor," he adds. Humans only ever wore rags. Yours are always ripped and stained with blood, but that's the way Master likes it. He loves to trace your flawless skin that should be scarred beyond repair after what he did the night before. Your clothing is the only reminder he has of what he's done. 

"I don't need armor," you respond with a newfound confidence that you are determined to hold on to.

"You're not invincible."

"Doc hasn't found my weakness yet." But you both knew the lie behind that statement. 

Sans grunts and tugs your leash towards the junction of moving walkways with cheesy-looking neon signs that told you the destinations: Lab, Market, Arena. You follow him onto the Arena walkway and watch the stone walls rush away into brick, sand, and the sound of fires that never stop burning. The Arena and the Lab were both built in an area known as Hotland. Monsters were never very creative with their naming of places, but they were always accurate. 

You enter the bottom level of the Arena by passing under the area known as The Bloody Arches. Rust colored hand prints of past survivors decorated the rough, sandstone columns. It is an old tradition before the shackles went back on, that the victorious humans and monsters would wipe their hands over their wounds and stain the archway before they were brought to market. A reminder that they existed, before they were sold to the highest bidder.

The Arena is a giant complex, but it's much larger than most in the stands realize. Below the arena floor is a small city of rooms, cells, gyms, and even a medical facility (mostly for monster competitors). Since your Master had taken a regular interest in you, you'd been put on a specific diet and forced to come here every day for routine exercise that he liked to call your "walk." Master prefers his play things fit for long hours of performance. Your magic may heal your body, but it can't hold up your legs when your muscles give into exhaustion. 

To your surprise, Sans didn't take you to your usual gym room. Instead, you follow him up the stairs to the Arena itself. You blink at the bright light of the underground's surface. It is hard to remember you're still somewhere inside a mountain when a bright orange haze decorates the "sky" above Hotland. You know the cause is magic, but you're still not knowledgeable enough on the science of it to know how it works. You've heard that other sections in the underground are in perpetual twilight and some are cast in complete night. You've only ever seen Hotland and the winter wonderland of the woods of Snowdin. In both, the "sun" never sets, you find "night" only in your cell or in the bedroom of your Master, who preferred a room with no windows. 

In the Arena, humans of all shapes and sizes are running around the wall just under the stands. Dust rises in their wake and gets in your eyes as they run past you both. They didn't speak. Only their steady breathing fills the air. One straggler wheezes as he stops for a moment near the entrance where Sans and you stand. 

"No breaks, human," a large, walking suit of armor yells. He whips the human's back until he yelps and continues running. "Keep that up and you won't make it to the next games. I'll just send you to the kitchens and your meat can feed the prisoners."

You know this suit of armor well. He is your Master's right hand, keeper of the Arena and trainer of all of your Master's prized fighters. His name is reduced to the number 01, and you've never seen him without his armor. You were, at one point, convinced that was all he was. After all, in a land of monsters, a walking suit of armor wouldn't be that strange. But after a very disappointing tournament where Master's humans all lost to Lady Muffet's, your Master stabbed him through a tiny gap in his armor. To his credit, 01 didn't cry out, he only apologized for his lax training and remained kneeling before your Master until he was satisfied. His blood puddled on the floor beneath him. When Master finally released him, you were surprised he could stand. 

"Clean that mess, Treasure," your Master ordered. "With your tongue."

As you bent over to obey, the tip of your tongue tasting the iron, sweat, and magic before you, he spanked you hard enough to thrust you forward. Your hands slipping on the viscous puddle and your face sliding into the mess as your Master tore away your rags and took you right there. It was one of the longest nights of your life. His frustration was not easily quelled. And when you couldn't keep up, he called for others... others that would be on the brink of death because they couldn't heal as you could. 

It was just another reason to get stronger. 

 "She's too small," 01's deep voice booms inside his black helmet, and breaks your train of thought.

"Size isn't everything," Sans' voice is almost deadly as he looks up at the other monster. You are sure 01 is blushing in embarrassment underneath that helmet. "One, you know what she can do."

"I know she can bleed," 01 shakes his head. "And fuck. It would seem she's already found her place in life."

"She wants to fight."

"We all want a lot of things..." 01's voice trails off. You wonder where his mind went to. 

"Please, sir," you bow your head. "My Master wishes me to learn how to fight. You're the best in the underworld. Who better to teach me?"

"The best... yes, I am that," he agrees, standing up a bit taller. It always astonishes you how kind words could move many monsters to action down here. It is an untouched weapon in this world of aggression. You would never have thought to use it until...

You look up at Sans as he unfastens your leash.

Until you realized kindness wasn't dead in this world. And if one of the most powerful monsters in the underground had the capacity for good, then many of the others must as well.

Sans shakes his head and leans in to whisper in your ear. "You may win him over, but the ones you're training with will not be as easily swayed."

The group of jogging humans came back around in another cloud of dust. This time you caught the looks of disgust and anger on their faces as they passed you. Even the straggled spit on the ground at your feet as he limped by. 

"Watch your back," Sans warns as he disappears into thin air, teleporting you alone with your new massive metal trainer. 

"Well? What are you waiting for, human? You're already four laps behind!"

**Author's Note:**

> Thanks for reading!
> 
> Tell me what you think so far in the comments or check out my [Tumblr](https://www.tumblr.com/blog/darkcrystaldemon).


End file.
